Meanwhile, the Congress said that that it is ready to go it alone in Uttar Pradesh in the Lok Sabha election.
Samajwadi Party president Akhilesh Yadav and Bahujan Samaj Party chief Mayawati will address a joint press meet in New Delhi on Saturday, amid talks of seat-sharing for Lok Sabha polls from which the Congress seems to be almost out.
The joint press conference at a posh hotel in Lucknow was announced on Friday by SP national secretary Rajendra Chaudhary and Bahujan Samaj Party national general secretary SC Misra.
The top leadership of both the parties had met in New Delhi recently to discuss broad parameters of an alliance to take on the Bharatiya Janata Party unitedly in the Lok Sabha elections.
The joint press conference will be the first after the parties gave contours of an electoral alliance ahead of the 2019 Lok Sabha elections.
The two party chiefs had given their "in principle" approval to the alliance, which has virtually shut its doors to the Congress in the state.
However, media coordinator of the Congress Rajiv Bakshi said that the party is ready to go it alone in Uttar Pradesh in the Lok Sabha election.
The Congress already has 45 seats in the Lok Sabha, more than any other regional player, Bakshi said.
"We are a political party and are ready to fight the coming elections alone in Uttar Pradesh," he said
"We are ready to take along like minded parties and they can come together with us," he added.
Sources said that both the SP and the BSP are planning to contest on 37 seats each out of the 80 on offer in Uttar Pradesh and plan to leave just two, Rae Bareli and Amethi, the bastions of Sonia Gandhi and Rahul Gandhi for the Congress.
Smaller parties like the Rashtriya Lok Dal and the Nishad Party are also likely to be in the alliance. In the 2014 Lok Sabha elections, the BJP and its allies had won 73 of the 80 seats in UP.
Congress leaders like PL Punia, who delivered Chhattisgarh to the Congress as its state in-charge, and Uttar Pradesh Congress Committee chief Raj Babbar are reportedly of the view that the Congress should not "be sheepish in alliance negotiations any more" and should seek its pound of flesh.
They cite the example of 2009 when the Congress romped home with 22 Lok Sabha seats in UP, surprising many prophets of doom.
They also say that with party chief Rahul Gandhi getting more "combative, direct and effective" in taking on the Modi juggernaut, the Congress stood better chances in going alone.
Over the week, Yadav and Mayawati also put out press statements that specifically referred to the word "gathbandhan".
Mayawati's press statement was in solidarity with Yadav amid reports that the CBI might question him on investigations into a mining scam that allegedly took place when he was chief minister.
"Don't be shaken," she advised him.
Yadav returned the favour when he put out a press release to condemn Prime Minister Narendra Modi's remarks at a rally in Agra on Mayawati, "forgetting" an attack on her by Samajwadi Party workers in 1995 for "political gains".
"The PM is scared of the alliance," said Yadav.
In Agra, Modi sought to drive a wedge between the Samajwadi Party and the Bahujan Samaj Party when he said that the two parties which could not see eye to eye were joining hands.
Last year, Yadav and Mayawati decided to bury their differences and pool in their resources to contest three bypolls and won all. It gave them hope that if they team up, they can pull voters away from the BJP.
The mahagathbandhan arithmetic had worked in the bypolls as a consolidation of OBC, Dalit and Muslim votes powered joint opposition candidates to victory in Gorakhpur, Phulpur and Kairana last year.
If they try to replicate their success in the 2019 national polls, it might upset the apple cart of the BJP, which recently lost three major state elections, feel analysts.
A senior BJP leader, when contacted, sought to play down the SP-BSP tie-up as "opportunistic" politics and expressed confidence that the saffron party will come out with flying colours on the plank of development as it believed in 'sab ka saath, sab ka vikas'.